Aedes albopictus in an important vector of dengue and dengue hemorrhagic fevers. From its presumed origin in southeast Asia, it has expanded its range from Madagascar to Hawaii. It was introduced into the continental United States last year and rapidly colonized 12 states posing a serious public health threat. The specific aims of the states posing a serious public health threat. The specific aims of the proposed project are to evaluate the vector competence for dengue fever of geographic strains of Aedes albopictus from the U.S. and abroad, determine the origin of U.S. populations and monitor changes in their breeding structure over time, and characterize genetic variation among populations of Aedes albopictus from throughout its range and between five species in the Aedes albopictus subgroup. The vector competence will be evaluated by cataloging variation in susceptibility to oral infection, disseminated infection and transmission among various strains, determining the degree to which these factors are under genetic control (their heritability), and if the heritability is found to be high, selecting for dengue refractory and susceptible strains of Ae. albopictus in order to determine the genetic basis of vector competency. Nuclear DNA amounts, allozymes and restriction maps of mitochondrial DNA will be used to determine origins of U.S. populations and to genetically characterize the same. UPGMA clustering and principal component analysis of DNA amounts and allele frequency data will be used to differentiate populations into subsets. Population specific restriction profiles of mitochondrial DNA will provide definitive information on maternal lineage. Information on allozyme differentiation within and among various cities in the U.S. over the five year period will provide insight into the dynamics of gene frequency changes that accompany colonization by Ae. albopictus. Molecular changes in genome organization and repetitive DNA fraction among various strains of Ae. albopictus and the four other subgroup species will be analysed through CoT curve analysis and cloning of satellite and rapidly reassociating DNA respectively. Chromosomal and reproductive differentiation will be assayed through studies of somatic and meiotic chromosomes and experimental hybridization. The long-term objectives are to utilize the genetic characterization of Ae. albopictus populations and four related species to determine the genetic basis of their vector competence to dengue, to understand the reasons for the rapid spread and to help design effective strategies for the containment/management of the species in U.S.